The embodiments herein relate to landing gear assemblies for aircraft and, more particularly, to an active landing gear assembly for rotary wing aircraft.
Rotary wing aircraft may experience a condition known as ground resonance. Ground resonance is an imbalance in the rotation of a rotor that causes an oscillation in phase with the frequency of the rocking of the helicopter on its landing gear. Existing solutions passively tune the dynamic response of the landing gear and/or undercarriage to move the resonant frequencies out of the region of concern. Existing solutions may also provide flight control law tuning in the flight control system to address ground resonance. Ground resonance may be precipitated by a hard landing, an asymmetrical ground contact, mechanical failure of a main rotor damper, or other causes.
Additionally, rotary wing aircraft experience challenges when landing on and taking off from sloped surfaces. When touching down on a sloped surface, as the up-slope landing gear touches down, this landing gear imparts a moment on the aircraft which must be counteracted with a moment from the rotor system. If such a moment is not provided by the rotor system, the rotorcraft will roll away from the slope and likely slide down the slope. Existing solutions seek to allow safe landings and the aircraft to “stick” to the slope by inputting rotor system moment to counteract the moment imparted by the landing gear the aircraft as the aircraft touches down on the slope.